Method of electrical metal-working



(No Model.) 2 Sheets-Sheet 1. G. D. BURTON.

METHOD OF ELECTRICAL METAL WORKING.

Patented May 17, 1892.

(No Model.) 2 SheetsSheet 2.

G. D. BURTON.

METHOD OF ELECTRIGAL METAL WORKING.

No. 475,182. Patented May'1'7, 1892.

C 5 III l 4 I c WITNESSES- UNITED STATES PATENT OFFICE.

GEORGE D. BURTON, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO THE ELECTRICALFORGING COMPANY, OF MAINE.

METHOD OF ELECTRICAL METAL-WORKING.

SPECIFICATION forming part of Letters Patent No. 475,182, dated May 17,1892. Application filed June 29,1891. Serial No. 397,829. (No model.)

To all whom it may concern:

Be it known that I, GEORGE D. BURTON, of Boston, in the county ofSufiolk and State of Massachusetts, have invented a new and usefulImprovement in Methods of Making Steel and Iron Tools, of which thefollowing is a specification.

Myinvention relates to methods of making tools or parts thereof of steeland iron; and it consists in certain new and useful steps and processesrelating thereto, substantially as hereinafter described and claimed.

The drawings show certain mechanisms by which my invention is carriedinto effect, as follows:

Figure 1 is a top plan View of an electriccurrent converter and asideelevation of the dynamo for heating thestee'l or iron. Fig. 2 is aside elevation of the converter. Fig. 3 is a front elevation of thesame. Figs. 4, 5, and G are enlarged detail views of one of the clamps,which secure the iron or steel in electric circuit while being heated,detached from its supporting-arm.

It has long been well known that in the process of drawing or rollingsteel and-iron out into bars and sheets their immediate surface wascondensed and rendered very homogeneous and capable of receiving a highpolish and retaining it against rust and wear. In the case ofcutting-blades formed out of such rolled or drawn steel it has also beenfound that when the extreme cutting-edge was formed of the lamination ofcondensed metal lying on the immediate surface it possessed a superiorsmoothness and keenness. The process of forging such rolled or drawnmetal bars into tools and utensils of various kinds has alwaysheretofore removed this lamination of condensed metal, due to therolling or drawing process, from its surface, first and chiefly in theform of scale burned oif by the fire, and, secondly, by its beingcrushed or forced into; the mass of metal underlying it on account ofthe forging heat being applied to the exterior of the sheet or bar andrendering that the'softest. The hammer ing and pressing of the metal indies therefore crushed and moved the more plastic molecules of metal onthe surface away from their contiguity and arrangement with relation toeach other which theyassumed in the drawing process and broke these up.My invention has for its object to avoid these disadvantages and impartto irregular-shaped forged tools and utensils or parts thereof theoriginal condensed lamination of metal which formed the surface of therolled or drawn sheet from which they were forged. I accomplish this byheating the internal part of the bar or sheet to a much higher degree ofheat than its outer surface and to such a degree of heat that theforging may be accomplished by merely bending around the exteriorlaminationof the metal to conform to the irregular-shaped exterior ofthe part ofthe finished tool or instrument which it becomes a portionof. This is accomplished by keeping the exterior cool enough withrelation to the more plastic interior of the metal to enable it to holdits original condensed laminated character, while the tool or instrumentis being shaped to the desired form under the die or hammer, and is alsoaccomplished by the heating being performed without the application ofany combustible or heating agent to the exterior of the bar or sheetbeing forged. Unless these two conditions are observed the inventioncannot be successfully practised. 'To carry out these purposes I beatthe bar or sheet of metal to be forged by an electric current in theopen air or in some surrounding. medium, which will keep its exteriorsurface much cooler than its internal substance, and I am careful not toraise the heat so high as to destroy the character of this surface,which was given to it in rolling or drawing the bar. I have discoveredthat it is possible to do this while also raising the heat of theinternal substance of the bar to a degree which allows'it to be forged,and, further, that the less heat of the laminated surface enables it toretain its character during the forging process and to conform to theexterior shape of the irregular tool or implement or part thereofforged, it

not being burned off in the forge by the combustion applied to it, andthe electrical-heating process being so speedy that it has not time tooxidize away while being brought to the required heat.

The electric-heating current must be of sufficient volume and voltageand be applied for a sufiicient time to heat the interior of the bar toa plastic forging temperature substantially even throughout the part tobe forged.

After the exterior surface reaches the temperature of oxidation thecurrent must be withdrawn within a short period of time before theoxidation substantially breaks ordestroys the skin of the metal. Thisperiod varies with difierent kinds of metal. For iron it should notgenerally exceed three minutes, and the current should preferably belessened or withdrawn within one minute. For brass the period of heatingafter oxidation begins may be somewhat longer.

I will now describe one form of the apparatus, which may be employed tocarry out my invention, although other forms may be used.

A is a dynamo of any approved construction, connected by the wires a ato the primary coil of the condenser C.

A is a small dynamo properly connected up to the coils of the dynamo Aas an exciter to energize the current of the latter. A rheostat orelectric regulator a is introduced into the circuit of the exciter,having the swinging arm at by which the strength of the exciter-currentmay beregnlated The secondary coil of the condenser terminates in theconductor-arms c c of great area in crosssection to accommodate theheavy current of low electro-motive force, which is delivered throughthem. The condenser is of any construction suitable to transform thehigh-tension-alternating current of the dynamo into the heavy current ofits secondary coil.

On the ends of the arms 0' c are attached two metal clamps d (1 Theseare formed, respectively, by the cam-roller d which is mounted on andpivots in the casing d, in such a position with relation to the end ofthe arm 0' (or 0 that by revolving it when any object is placed betweenthem itwill squeeze that object forcibly against the arm. The arm androller at this point are preferably made of or faced with copper. Theroller is also provided with a handle (P, by which to revolve it.

The clamps d and d are made with area enough to their faces, which graspthe bar to be heated, to prevent undue heatin g of the latter where theytake hold of its surface. This is very important, for if the area orconductivity of these clamps be too small the bar will be heated thehighest on the surface where they grasp it.

The bar to be heated is placed in the clampsd (P, and they are closeddown upon it and the current turned on. The size of this bar is such(say one inch wide and onefourth inch thick) with relation to theconductivity of the secondary coil and the arins c c that it presents acomparativly high resistance to the current passing through it, and thusbecomes rapidly heated to a forging heat in its internal substance. Theexternal surface of the bar being exposed to the air remains at a muchlower temperature and preserves its essential homogeneous character.\Vhile the bar is in this condition I remove it from the clamps (l' dand subject it to the forging process in a die so constructed as not tobreak the external shell by repeated blows, but merely to compress orbend it into the exterior form of the article or part thereof beingforged. I may do this by a die in a press or byone mounted in adrop-hammer heavy enough to compress the article into the desired shapeunder its blows. The movements of the excess of metal being forged willbe found to be chiefi y at the more plastic center of the'heated bar orstrip and only a bending movement on its surface. because the hotter andmore plastie metal at the center yields more easily. In this waytools-such as table-knives, chisels, angers, &c.-may be forged up eitheron the blade part or the handle part or on both blade and handle parts,so as to have upon them the smoothness and polish and homogeneoussurface that was originally formed upon the surface of the bars orsheets of metal from which they were forged. I am thus enabled to imparta superior finish to the surfaces of such tools and render them capableof resisting rust and wear in a su perior degree, and where the extremecut ting-edge can be formed of this surface part of the metal, as in thecase of chisels, it has a superior smoothness and keenness. The handlesof such forged tools can also be finished by polishing or nickel platingwith a trifling expense compared with the present methods.

In heating the metal by the electric current, as described, it should beremembered that as'the exterior of the bar or sheet is kept cooler thanthe internal parts the color of the heated surface will indicate a muchlower temperature when the metal is ready to forge than with the methodsof forging now employed; but while this color cannot be readilydescribed in words it will be easilyunderstood by the expertforge-operator by a little practice.

That I claim as new and of my invention is- The method of making a metalforging, which consists in subjecting a rolled or drawn bar or sheet tobe forged to the action of an electric heating current until itsinterior is raised to a plastic forging heat and maintaining thetemperature of its exterior so far below that of the interior as topreserve its form and homogeneous character, said heating operationbeing performed within a pethe surface of the finished article or forgedriod which will avoid the destruction of the part thereof withoutbreaking or destroying external skin of the metal by oxidation, and saidskin, substantially as set forth.

then forging or shaping the bar or sheet into GEO. D. BURTON. thedesired irregular shape or article by Witnesses: bending or shaping theexternal skin of the DAVID HALL RICE,

bar over the internal plastic metal to form CHAS. J. TOLANI).

